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The optic neuroepithelial continuum of vertebrate eye develops into three differentially growing compartments: the retina, the ciliary margin (CM), and the retinal pigment epithelium (RPE). Neurofibromin 2 (Nf2) is strongly expressed in slowly expanding RPE and CM compartments, and the loss of mouse Nf2 causes hyperplasia in these compartments, replicating the ocular abnormalities seen in human NF2 patients. The hyperplastic ocular phenotypes were largely suppressed by heterozygous deletion of Yap and Taz, key targets of the Nf2-Hippo signaling pathway. We also found that, in addition to feedback transcriptional regulation of Nf2 by Yap/Taz in the CM, activation of Nf2 expression by Mitf in the RPE and suppression by Sox2 in retinal progenitor cells are necessary for the differential growth of the corresponding cell populations. Together, our findings reveal that Nf2 is a key player that orchestrates the differential growth of optic neuroepithelial compartments during vertebrate eye development.
Copyright © 2017 Elsevier Inc. All rights reserved.
Cytochrome P450 (P450, CYP) 21A2 is the major steroid 21-hydroxylase, converting progesterone to 11-deoxycorticosterone and 17α-hydroxyprogesterone (17α-OH-progesterone) to 11-deoxycortisol. More than 100 variants give rise to congenital adrenal hyperplasia (CAH). We previously reported a structure of WT human P450 21A2 with bound progesterone and now present a structure bound to the other substrate (17α-OH-progesterone). We found that the 17α-OH-progesterone- and progesterone-bound complex structures are highly similar, with only some minor differences in surface loop regions. Twelve P450 21A2 variants associated with either salt-wasting or nonclassical forms of CAH were expressed, purified, and analyzed. The catalytic activities of these 12 variants ranged from 0.00009% to 30% of WT P450 21A2 and the extent of heme incorporation from 10% to 95% of the WT. Substrate dissociation constants () for four variants were 37-13,000-fold higher than for WT P450 21A2. Cytochrome , which augments several P450 activities, inhibited P450 21A2 activity. Similar to the WT enzyme, high noncompetitive intermolecular kinetic deuterium isotope effects (≥ 5.5) were observed for all six P450 21A2 variants examined for 21-hydroxylation of 21--progesterone, indicating that C-H bond breaking is a rate-limiting step over a 10-fold range of catalytic efficiency. Using UV-visible and CD spectroscopy, we found that P450 21A2 thermal stability assessed in bacterial cells and with purified enzymes differed among salt-wasting- and nonclassical-associated variants, but these differences did not correlate with catalytic activity. Our in-depth investigation of CAH-associated P450 21A2 variants reveals critical insight into the effects of disease-causing mutations on this important enzyme.
© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.
How metabolic pathways required for epidermal tissue growth and remodeling influence the ability of keratinocytes to survive stressful conditions is still largely unknown. The mechanistic target of rapamycin complex 2 (mTORC2) regulates growth and metabolism of several tissues, but its functions in epidermal cells are poorly defined. Rictor is an adaptor protein essential for mTORC2 activity. To explore the roles of mTORC2 in the epidermis, we have conditionally deleted rictor in mice via K14-Cre-mediated homologous recombination and found that its deficiency causes moderate tissue hypoplasia, reduced keratinocyte proliferation and attenuated hyperplastic response to TPA. Noteworthy, rictor-deficient keratinocytes displayed increased lifespan, protection from senescence, and enhanced tolerance to cellular stressors such as growth factors deprivation, epirubicin and X-ray in vitro and radioresistance in vivo. Rictor-deficient keratinocytes exhibited changes in global gene expression profiles consistent with metabolic alterations and enhanced stress tolerance, a shift in cell catabolic processes from glycids and lipids to glutamine consumption and increased production of mitochondrial reactive oxygen species (ROS). Mechanistically, the resiliency of rictor-deficient epidermal cells relies on these ROS increases, indicating stress resistance via mitohormesis. Thus, our findings reveal a new link between metabolic changes and stress adaptation of keratinocytes centered on mTORC2 activity, with potential implications in skin aging and therapeutic resistance of epithelial tumors.
OBJECTIVES - We compared the utility of membrane-associated guanylate kinase, WW and PDZ domain-containing protein 2 (MAGI-2) and α-methylacyl CoA (AMACR) by immunohistochemistry in diagnosing prostatic adenocarcinoma.
METHODS - Seventy-eight radical prostatectomies were used to construct three tissue microarrays with 512 cores, including benign prostatic tissue, benign prostatic hyperplasia, high-grade prostatic intraepithelial neoplasia (HGPIN), and adenocarcinoma. AMACR and MAGI-2 immunohistochemistry were evaluated by visual and image analysis.
RESULTS - MAGI-2 and AMACR were significantly higher in adenocarcinoma and HGPIN compared with benign tissue. At H-score cutoffs of 300 and 200, MAGI-2 was more accurate in distinguishing benign from malignant glands than AMACR. Areas under the curve by image and visual analysis were 0.846 and 0.818 for MAGI-2 and 0.937 and 0.924 for AMACR, respectively. The accuracy of MAGI-2 in distinguishing benign from malignant glands on the same core was higher (95% vs 88%).
CONCLUSIONS - MAGI-2 could represent a useful adjunct for diagnosis of prostatic adenocarcinoma, especially when AMACR is not discriminatory.
© American Society for Clinical Pathology, 2016. All rights reserved. For permissions, please e-mail: email@example.com.
BACKGROUND - Benign prostatic hyperplasia (BPH) is treated with 5α-reductase inhibitors (5ARI). These drugs inhibit the conversion of testosterone to dihydrotestosterone resulting in apoptosis and prostate shrinkage. Most patients initially respond to 5ARIs; however, failure is common especially in inflamed prostates, and often results in surgery. This communication examines a link between activation of NF-κB and increased expression of SRD5A2 as a potential mechanism by which patients fail 5ARI therapy.
METHODS - Tissue was collected from "Surgical" patients, treated specifically for lower urinary tract symptoms secondary to advanced BPH; and, cancer free transition zone from "Incidental" patients treated for low grade, localized peripheral zone prostate cancer. Clinical, molecular and histopathological profiles were analyzed. Human prostatic stromal and epithelial cell lines were genetically modified to regulate NF-κB activity, androgen receptor (AR) full length (AR-FL), and AR variant 7 (AR-V7) expression.
RESULTS - SRD5A2 is upregulated in advanced BPH. SRD5A2 was significantly associated with prostate volume determined by Transrectal Ultrasound (TRUS), and with more severe lower urinary tract symptoms (LUTS) determined by American Urological Association Symptom Score (AUASS). Synthesis of androgens was seen in cells in which NF-κB was activated. AR-FL and AR-V7 expression increased SRD5A2 expression while forced activation of NF-κB increased all three SRD5A isoforms. Knockdown of SRD5A2 in the epithelial cells resulted in significant reduction in proliferation, AR target gene expression, and response to testosterone (T). In tissue recombinants, canonical NF-κB activation in prostatic epithelium elevated all three SRD5A isoforms and resulted in in vivo growth under castrated conditions.
CONCLUSION - Increased BPH severity in patients correlates with SRD5A2 expression. We demonstrate that NF-κB and AR-V7 upregulate SRD5A expression providing a mechanism to explain failure of 5ARI therapy in BPH patients. Prostate 76:1004-1018, 2016. © 2016 Wiley Periodicals, Inc.
© 2016 Wiley Periodicals, Inc.
Membrane-associated guanylate kinase, WW and PDZ domain-containing protein 2 (MAGI-2) is a scaffolding protein that links cell adhesion molecules, receptors, and signaling molecules to the cytoskeleton and maintains the architecture of cell junctions. MAGI-2 gene rearrangements have recently been described in prostate cancer. We studied the immunohistochemical expression of MAGI-2 protein in prostate tissue. Seventy-eight radical prostatectomies were used to construct 3 tissue microarrays consisting of 512 cores, including benign tissue, benign prostatic hyperplasia, high-grade prostatic intraepithelial neoplasia (HGPIN), and adenocarcinoma, Gleason patterns 3 to 5. Immunohistochemistry for phosphatase and tensin homologue (PTEN) and double-stain MAGI-2/p63 was performed and analyzed by visual and image analysis, the latter as percent of analyzed area (%AREA), and mean optical density multiplied by %AREA (STAIN). By visual and image analysis, MAGI-2 was significantly higher in adenocarcinoma and HGPIN compared with benign (benign versus HGPIN P < .001; benign versus adenocarcinoma, P < .001). HGPIN and adenocarcinoma did not significantly differ by either modality. Using visual intensity to distinguish benign tissue and adenocarcinoma, a receiver operating curve yielded an area under the curve of 0.902. A STAIN threshold of 1470 yielded a sensitivity of 0.66 and specificity of 0.96. There was a significant correlation between PTEN and MAGI-2 staining for normal and benign prostatic hyperplasia, but this was lost in HGPIN and cancer. We conclude that MAGI-2 immunoreactivity is elevated in prostate cancer and HGPIN compared with normal tissue, and suggest that MAGI-2 may contribute to prostate carcinogenesis. This is the first report of MAGI-2 staining by immunohistochemistry in prostate cancer.
Copyright © 2016 Elsevier Inc. All rights reserved.
BACKGROUND - Benign prostatic hyperplasia (BPH) is a common, chronic progressive disease. Inflammation is associated with prostatic enlargement and resistance to 5α-reductase inhibitor (5ARI) therapy. Activation of the nuclear factor-kappa B (NF-κB) pathway is linked to both inflammation and ligand-independent prostate cancer progression.
METHODS - NF-κB activation and androgen receptor variant (AR-V) expression were quantified in transition zone tissue samples from patients with a wide range of AUASS from incidental BPH in patients treated for low grade, localized peripheral zone prostate cancer to advanced disease requiring surgical intervention. To further investigate these pathways, human prostatic stromal and epithelial cell lines were transduced with constitutively active or kinase dead forms of IKK2 to regulate canonical NF-κB activity. The effects on AR full length (AR-FL) and androgen-independent AR-V expression as well as cellular growth and differentiation were assessed.
RESULTS - Canonical NF-κB signaling was found to be upregulated in late versus early stage BPH, and to be strongly associated with non-insulin dependent diabetes mellitus. Elevated expression of AR-variant 7 (AR-V7), but not other AR variants, was found in advanced BPH samples. Expression of AR-V7 significantly correlated with the patient AUASS and TRUS volume. Forced activation of canonical NF-κB in human prostatic epithelial and stromal cells resulted in elevated expression of both AR-FL and AR-V7, with concomitant ligand-independent activation of AR reporters. Activation of NF-κB and over expression of AR-V7 in human prostatic epithelial cells maintained cell viability in the face of 5ARI treatment.
CONCLUSION - Activation of NF-κB and AR-V7 in the prostate is associated with increased disease severity. AR-V7 expression is inducible in human prostate cells by forced activation of NF-κB resulting in resistance to 5ARI treatment, suggesting a potential mechanism by which patients may become resistant to 5ARI therapy.
© 2015 Wiley Periodicals, Inc.
A functional complex consisting of androgen receptor (AR) and forkhead box A1 (FOXA1) proteins supports prostatic development, differentiation, and disease. In addition, the interaction of FOXA1 with cofactors such as nuclear factor I (NFI) family members modulates AR target gene expression. However, the global role of specific NFI family members has yet to be described in the prostate. In these studies, chromatin immunoprecipitation followed by DNA sequencing in androgen-dependent LNCaP prostate cancer cells demonstrated that 64.3% of NFIB binding sites are associated with AR and FOXA1 binding sites. Interrogation of published data revealed that genes associated with NFIB binding sites are predominantly induced after dihydrotestosterone treatment of LNCaP cells, whereas NFIB knockdown studies demonstrated that loss of NFIB drives increased AR expression and superinduction of a subset of AR target genes. Notably, genes bound by NFIB only are associated with cell division and cell cycle. To define the role of NFIB in vivo, mouse Nfib knockout prostatic tissue was rescued via renal capsule engraftment. Loss of Nfib expression resulted in prostatic hyperplasia, which did not resolve in response to castration, and an expansion of an intermediate cell population in a small subset of grafts. In human benign prostatic hyperplasia, luminal NFIB loss correlated with more severe disease. Finally, some areas of intermediate cell expansion were also associated with NFIB loss. Taken together, these results show a fundamental role for NFIB as a coregulator of AR action in the prostate and in controlling prostatic hyperplasia.
Homozygous Mnx1 mutation causes permanent neonatal diabetes in humans, but via unknown mechanisms. Our systematic and longitudinal analysis of Mnx1 function during murine pancreas organogenesis and into the adult uncovered novel stage-specific roles for Mnx1 in endocrine lineage allocation and β-cell fate maintenance. Inactivation in the endocrine-progenitor stage shows that Mnx1 promotes β-cell while suppressing δ-cell differentiation programs, and is crucial for postnatal β-cell fate maintenance. Inactivating Mnx1 in embryonic β-cells (Mnx1(Δbeta)) caused β-to-δ-like cell transdifferentiation, which was delayed until postnatal stages. In the latter context, β-cells escaping Mnx1 inactivation unexpectedly upregulated Mnx1 expression and underwent an age-independent persistent proliferation. Escaper β-cells restored, but then eventually surpassed, the normal pancreatic β-cell mass, leading to islet hyperplasia in aged mice. In vitro analysis of islets isolated from Mnx1(Δbeta) mice showed higher insulin secretory activity and greater insulin mRNA content than in wild-type islets. Mnx1(Δbeta) mice also showed a much faster return to euglycemia after β-cell ablation, suggesting that the new β-cells derived from the escaper population are functional. Our findings identify Mnx1 as an important factor in β-cell differentiation and proliferation, with the potential for targeting to increase the number of endogenous β-cells for diabetes therapy.
© 2015. Published by The Company of Biologists Ltd.